lineRatio: size of line-height relative to the font-size. defaults to 1.45

flowtype(document.body,{

maxWidth:'800px',// can be a CSS value or a Number

minWidth:'300px',

lineRatio:1.45,

min:14,

max:22

})

In the above example when the document is 800px or wider flowtype will set the font size to 22px. When the document is 300px or less it will be set the font size to 14px. And when the document is at any width between 300px and 800px it will set the font size to match proportionally. e.g. if the document was 500px wide thats 40% of the distance from 300px to 800px so the font size will be set to 40% of the distance from 14px to 22px which is 17.2px.

Note: flowtype sets font size in pixels on the el you passed in. So you need to ensure that any children inside el have their font set in ems. Unless you want their font size to stay fixed.